As known, linear electric actuators for activating vehicle steering systems comprise a stem, whose ends are associated to the wheels of the vehicle by means of leverages.
Translating said stem towards one or the other wheel enables steering the vehicle by inclining the wheels with respect to the direction of advancement in one direction or the other.
A known solution provides for that the translation of the stem be carried out through a recirculating ball screw system.
In particular, an external thread obtained in a portion of the stem is coupled, by interposing balls, to a holder nut and the translation of the stem is carried out by driving the holder nut in rotation by means of an electric motor.
This screw-holder nut coupling is generally contained in a hermetically closed casing suitable to contain a lubricating fluid, while the ends of the stem project outside so as to be connected to the leverages of the steering.
Thus, these ends are exposed to direct contact with the external bodies, dirt and, in given applications, with the atmospheric agents.
The stem should be made of material capable of guaranteeing a rather high surface hardness so as avoid wear due to external agents.
At the same time, the stem should also be made of a material that can guarantee the machinability features required to obtain an external thread with the right tolerances (very stringent in case of recirculating ball screw systems).
In addition, were we also to consider the fact that the stem should be made in a single piece in order to guarantee suitable static structural resistance and stress strength, it is clear how generally challenging it is to simultaneously meet all the aforementioned needs.
An object of the present invention is to overcome this drawback of the prior art through a solution that is simple, rational and inexpensive.
These objects are attained by the characteristics of the invention, which are outlined in the independent claims.
The dependent claims outline preferred and/or particularly advantageous aspects of the invention.